Rule source on GitHub

DowngradeEnumToConstantListClassRector

Downgrade enum to constant list class

-enum Direction
+class Direction
 {
-    case LEFT;
+    public const LEFT = 'left';

-    case RIGHT;
+    public const RIGHT = 'right';
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp80\Rector\Enum_\DowngradeEnumToConstantListClassRector;

return RectorConfig::configure()
    ->withRules([
        DowngradeEnumToConstantListClassRector::class,
    ]);